Up to one-third of a building's heat is lost thrugh windows. Double and triple glass panes are now frequently specified to combat this heat loss. Many manufacturers are attempting to increase the "R" value (resistance to heat conduction) int heir window sashes and mullions. Some metal window sashes are now fabricated with thermal breaks, or gaps between opposed metal sash components, to reduce heat conduction as well as condensation on the room side of the sash. Wood window sashes are also being specially designed to reduce heat loss and condensation. Wood is not as dimensionally stable as metal and it can dry out and warp. This can produce cracks allowing air infiltration and heat loss.
Improved windows, fabricated from lineals having a fibrous glass wool core and a hardened resinous or polymeric outer surface are disclosed in U.S. Pat. Nos. 4,553,364 issued to Legg et al. and 4,640,065 issued to Harris et al. Further, U.S. Pat. No. 4,681,772 issued to Carter et al. discloses a system for molding or fabricating such lineals.
One problem common to all multipaned window systems, i.e., wood, metal or composite, is controlling moisture between the panes. Excess moisture in the cavity between the panes results in a foggy window. Some try hermetically sealing the cavity between the panes. Such seals are prone to failure, which requires replacement of the unit. Others adopted various systems for venting the cavity to the atmosphere. such vents can permit dirt and insects to enter the cavity, which requires cleaning of the interior of the unit. There is a need for improved window assemblies and door assemblies to vent window cavities to the outside atmosphere while prohibiting dirt and insects from entering the window cavity.